1. Field of the Invention
The invention relates to clutches, and in particular to vehicle clutch assemblies. More particularly, the invention relates to a friction plate mounted within the clutch assembly having a unique shock absorbing damper spring with increased stiffness without an increase in size, to reduce damaging vehicle driveline shock and clutch damage. The invention also relates to such a unique spring construction in which a coil spring is encapsulated in an elastomer to increase its loading characteristics.
2. Description of the Prior Art
There are numerous types, styles and sizes of friction clutches having a countless number of various components to increase the efficiency, wear and clutch operation in both manual and automatic vehicle transmissions. Many clutch constructions have a friction drive plate and a plurality of resilient elements to rotationally couple the drive plate to a hub member. These resilient members absorb much of the engagement shock and torque when the friction elements, which are attached to the drive plate, are brought into coupling engagement with similar friction elements on a flywheel, pressure plate, etc., on the driving member of the clutch. These resilient members reduce considerably the shock on the vehicle driveline which includes the universal joint, transmission, drive shaft and differential. These resilient elements also tend to reduce clutch chatter.
A number of clutch friction plate designs have been developed which use various arrangements of resilient coupling elements to achieve the shock absorbing and chatter reducing effects. The most general type of resilient element used is a coil compression spring, such as shown in U.S. Pat. Nos. 2,058,575, 2,076,373 and 2,613,785. Other clutch constructions have used a resilient rubber insert or bushing in place of a coil spring for this purpose. Examples of these constructions are shown in U.S. Pat. Nos. 1,818,610, 2,299,010 and 3,897,859.
Many of these known clutch friction plate constructions which use either a spring or rubber bushing as the resilient member, have proved satisfactory for usual torques and shocks encountered during clutch coupling engagement. Problems, however, have developed in certain clutch constructions, especially when used in high performance racing vehicles. These racing vehicle clutches develope excessive torques and shocks which result in excess relative rotation between the hub member and friction drive plate. This excess rotation may cause the coupling springs to bottom out, resulting in destruction of the springs or shearing and damaging of the hub member or stop pins which are used in many such clutch constructions. Much of this excess torque and shock is transmitted to the vehicle driveline, causing damage and maintenance problems to the vehicle.
In order to reduce this clutch damage, it is necessary to increase the stiffness of the rotational coupling springs. This is difficult in many clutch designs in that there is insufficient room for additional or bigger springs, and in most designs the springs which are being used have the maximum amount of stiffness which is feasible.
Therefore, the need has existed for an improved resilient member for rotationally coupling together the hub member and drive plate of a clutch friction plate which has stiffer shock absorbing and loading characteristics without increasing the physical size and configuration of the spring component. No clutch construction of which I am aware uses a coil compression spring encapsulated in an elastomer to achieve these results.